[relax-ng] New compact syntax draft

I (finally) did a new compact syntax draft:

 http://www.thaiopensource.com/oasis/compact-20020822.html

This includes the following changes

- Rename "externalRef" to "external" as we agreed in a telcon a long time
ago

- Fixes things found by Makoto as specified in my last message

- Adds a new Section 6; this depends on a new paragraph in A.1 that
specifies a correct RELAX NG Compact Syntax schema.

James